Short term effects of urban air pollution on respiratory health in Milan, Italy, 1980-89

Study objective - To investigate the association between daily urban air pollution and acute effects on respiratory health. Study design - Time series analysis following the procedure defined in the APHEA protocol. Setting - City of Milan, Italy, from 1980-89. Two air pollutants, total suspended particulates (TSP) and sulphur dioxide (SO,), and two health outcomes, deaths and hospital admissions were considered. The last was analysed according to two age groups. Subjects - Daily deaths and general hospital admissions for respiratory causes in residents who died in Milan or were admitted to local hospitals in that city. Main results - There was an increased risk of respiratory death and of hospital admission associated with increased concentrations of SO, and TSP. The relative risks were similar for both pollutants, and were higher for respiratory deaths than for hospital admissions. No changes in relation to season were seen in the SO, effect on respiratory deaths, but there was a suggestion of a higher effect on hospital admissions in the cool months. The seasonal pattern of the TSP effect was inconsistent: for mortality it was higher in the warm period while for hospital admissions it seemed to be higher in the cool months. This last result might be due to chance, although some role could have been played by the hospital admission data on all general admissions for respiratory causes (ICD-9: 460-519) as these are a much less specific end point. Conclusion - In Milan, a positive association was found between the daily SO, or TSP concentrations and the number of deaths or hospital admissions for respiratory causes. This confirms results from other European and North American cities.